Apparatuses and methods for semiconductor die heat dissipation

ABSTRACT

Apparatuses and methods for semiconductor die heat dissipation are described. For example, an apparatus for semiconductor die heat dissipation may include a substrate and a heat spreader. The substrate may include a thermal interface layer disposed on a surface of the substrate, such as disposed between the substrate and the heat spreader. The heat spreader may include a plurality of substrate-facing protrusions in contact with the thermal interface layer, wherein the plurality of substrate-facing protrusions are disposed at least partially through the thermal interface layer.

BACKGROUND

The evolution of electronics is forcing component manufacturers todevelop smaller devices while providing greater functionality and speed.The combination of these size and operational goals may lead toincreases in internal heat generation. The increase in heat generationmay be due to obstructed or inefficient thermal paths in combinationwith higher operating power consumption. For the components to continueto provide the performance desired, the extra heat may need to bedissipated. At a time when components (and the systems including thecomponents) were larger, dissipation of any extra heat may have beenmore easily accomplished due to heat dissipating bulk materials and/orthe air flow around the components. Currently, however, small, highpowered devices and components containing multiple co-packaged die maybenefit from packaging that provides higher thermal conductivity pathsfor dissipating the heat generated within such devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an example illustration of a heat spreader and semiconductordie stack combination according to the present disclosure.

FIG. 1B is an example illustration of a die, thermal interface layer,heat spreader relationship according to the present disclosure.

FIG. 2A is another example illustration of a heat spreader andsemiconductor die stack combination according to the present disclosure

FIG. 2B is another example illustration of a die, thermal interfacelayer, and heat spreader relationship according to the presentdisclosure.

FIG. 3 is an example illustration of a die according to the presentdisclosure.

FIGS. 4A and 4B are example illustrations of a heat spreader accordingto the present disclosure.

DETAILED DESCRIPTION

Apparatuses and methods for heat extraction from packaged semiconductordevices are disclosed herein. Certain details are set forth below toprovide a sufficient understanding of embodiments of the disclosure.However, it will be clear to one having skill in the art thatembodiments of the disclosure may be practiced without these particulardetails. Moreover, the particular embodiments of the present disclosuredescribed herein are provided by way of example and should not be usedto limit the scope of the disclosure to these particular embodiments. Inother instances, well-known circuits, control signals, timing protocols,and software operations have not been shown in detail in order to avoidunnecessarily obscuring the disclosure.

As noted, thermal management of semiconductor devices is an everincreasing concern and due in part to combinations of device size andpower consumption. Other factors may also contribute to thermalconcerns, such as multiple die packaged together for example. Heatextraction barriers such as multiple interfaces may contribute to theproblems of multiple co-packaged die. At elevated operating levels, theoverall heat generated by multiple co-packaged die may increase. Such anincrease in heat generation may be due to the proximity of severalco-packaged die exacerbating heat conduction and adding to an operatingenvironment at an elevated temperature. For example, a co-package stackof die may present a difficult heat extraction configuration due to themultiple interfaces the heat may need to travel before reaching anexternal surface of the package for dissipation. Additionally, lateralheat extraction may also be limited due to die packaging configurations.The additional heat, if not efficiently removed from the stack of die,may cause one or more die in the stack to experience temperatures abovetheir specified limits. Such thermal problems may lead to malfunctioningor inoperable devices.

Packaging may play a role in enhancing heat extraction. Heat sinks maybe added to packaging in an effort to dissipate heat more efficiently.Packaging materials may be designed to have increased thermalconductivity characteristics aimed at improving heat dissipation. Thesepackaging materials may include metal fillers to improve thermalconductivity, for example. Most of these approaches, however, may bemore focused external to the package or minimally related to the packageitself. More package-centric approaches may focus on supplying heatconduction paths from die to package, but these approaches may belimited by the material used for the die and package or space limited.

In the case of a multi-die package, for example, the extraction of heatmay be inhibited due to the many interfaces through which the heat mayneed to travel. The interfaces may impede the flow of heat in directionsperpendicular to the die surface, but may also impede planar heat flowwithin a die. The interfaces may be due to die fabrication, e.g., manylayers of metal and passivation layers built up on an active surface ofthe die, and/or to the die being stacked, e.g., multiple die stacked ontop of one another. The interfaces may cause the heat flow to be reduceddue to reflection and the materials of the die may reduce heat flow dueto variations in thermal conductivity. Further, the distance from a heatgenerating source, e.g., an active area of a die, to a heat-dissipatingpackaging surface may also reduce heat dissipation. Moreover, lowthermal conductivity of the various package materials may also adverselyaffect heat dissipation.

One solution to increase the heat extraction from a co-packaged diestack may be to package the die stack with a conformal heat spreaderthat includes internally-facing protrusions. The internally-facingprotrusions may be in close proximity to and/or touching one or more diein the die stack. The internally-facing protrusions may be die stackfacing and may provide for increased heat spreader surface area toprovide an improved thermal path. The internally-facing protrusions maycontact or be in close proximity to the top die of the stack and to oneor more other die of the stack, such as the bottom die. The reduceddistance from the die surface to a bottom surface of each of theprotrusions may provide improved thermal pathways from the die to thepackage/heat spreader. A bottom surface of the protrusions along withsides of the protrusions may reduce the distance through which heat maytravel from the die surface to the heat spreader. The reduced distancebetween the die surface and heat spreader may include a small volume(e.g., a thin layer) of a thermal interface material that is formedbetween the heat spreader and the die. An alternative solution mayinvolve the protrusions of the heat spreader contacting or coming intoclose proximity to thermal dissipation pads formed on the backside ofone or more die of the die stack. The “backside” of the die may be aface of the die opposite a face of the die that includes the activeelements, e.g., transistors and logic gates, which may be referred to asthe “front side” of the die. The thermal dissipation pads may furtherenhance heat dissipation of the die stack.

FIG. 1A is an example illustration of a heat spreader and semiconductordie stack combination 100 according to the present disclosure. Thecombination 100 may represent a semiconductor die stack packaged with aheat spreader. In some embodiments, the heat spreader may be a conformallid. The combination 100 may include a heat spreader 102, a plurality ofsemiconductor die 106 A-D, a semiconductor die 108, and a base 110,which may be configured to enhance thermal dissipation of the stack ofdie 106 A-D and 108. The heat spreader 102 may include die-facingprotrusions that may allow for increased dissipation of heat from one ormore of the die 106 A-D and/or 108. The base 110 may be a printedcircuit board (PCB) or a base of a semiconductor package, for example.The base 110 is a non-limiting aspect of the present disclosure, and anytype of base would fall within the scope of the present disclosure. Theheat spreader 102 may be connected to the base 110 by adhesion bonds112. The combination 100 may be included in any electronics host systemsuch as portable electronics, smartphones, laptop computers, desktopcomputers, etc. In one non-limiting example, the combination 100 may bea memory module including multiple semiconductor memory die and aninterface die.

In a non-limiting example, each of the plurality of die 106 A-D may be amemory die, such as non-volatile or volatile memory die. The die 108 maybe an interface die or a logic die. The stack of die, including theplurality of die 106 A-D and the die 108, may be interconnected withthrough-via interconnects (not shown), which may be a common bus forcommand and data signals to propagate within the stack of die. Thecommand and data signals may be externally provided to the stack of dieby the host and data may be provided to the host in response.Additionally, the die 108 may receive data and command signals from oneor more external components, and in response provide the data/commandsignals to a target die 106 of the plurality of die 106 A-D.

In the example shown in FIG. 1A, the die 108 is depicted as being largerthan the die 106 and this depiction may be for illustrative purposesonly and is non-limiting. The difference in size may be due to variousfunctions the die 108 performs and the respective circuits used for suchfunctions. The die 108 may include logic circuits and communicationcircuits, which may generate heat due to the power levels at which thedie operates. Heat generated by the die 108, especially if generateddirectly under the die 106 D, may be difficult to dissipate. Thedifficulty in dissipation may be due to the distance from a heatgenerating area of the die 108 and a path taken by the heat from heatgenerating area to the heat spreader 102. In general, heat generated byany or all of the plurality of die 106 A-D and 108 may be difficult toextract due to the various interfaces and paths the heat must travelfrom a respective die to the heat spreader 102.

The combination 100 may further include a thermal interface layer 104disposed between the die 106 A, exposed edges of the die 108 and theheat spreader 102. The thermal interface layer 104 may be included toassist with heat transfer from the die stack to the heat spreader 102,and may also assist in mounting, e.g., attaching, the heat spreader 102to the die stack. The thermal interface layer 104 may be an epoxymaterial that may or may not include metal fillers, such as indium orgallium. The metal fillers may be included to enhance thermalconduction, and may be indium or gold. The thickness of the thermalinterface layer 104 may be from 20 to 50 microns, which may be dependentupon fabrication process and/or due to normal variations in thefabrication process. The thermal interface layer 104 may have a thermalconductivity rating of 2 W/mK to 10 W/mK, and the variation in thermalconductivity may be due to the presence, or lack thereof, of the fillermaterials present.

As discussed above, one solution to the problem of dissipating heat froma stack of semiconductor die may include decreasing a distance from aheat sink to a surface of a die. An example embodiment of the solutionmay involve adding a plurality of protrusions 114 to the heat spreader102. The plurality of protrusions may be internally-facing, e.g.,die-facing, such as depicted by the protrusions 114 shown in FIG. 1A.The protrusions 114 may be partially or fully disposed within, e.g.,embedded into and/or extending through, the thermal interface layer 104such that a bottom face of one or more of the protrusions 114 are inclose proximity to the top of the die 106 A and the exposed portions ofthe die 108. To further illustrate, if the thermal interface layer 104is 50 microns thick, then a bottom face of one or more protrusions 114disposed into the thermal interface layer may be substantially proximateto the surface of the die, e.g., within 10 microns or less of the diesurface. In this configuration, the thickness of the thermal interfacelayer 104 between the surface of a protrusion and the die surface isless relative to the 50 micron thickness of the thermal interface layer104 present in the spaces between the protrusions 114. As such, theremay be a reduction in volume of the thermal interface layer 104 betweenthe protrusions 114 and the die 106 A and/or the exposed portions of thedie 108. This decrease in volume of the thermal interface layer 104 mayimprove the heat path, e.g., reduce the amount of the thermal interfacelayer 104 the heat must travel before reaching the heat spreader 102.Additionally or alternatively, the bottom surface of one or more of theprotrusions 114 may make direct, physical contact with the top of thedie 106 A and/or the exposed portions of the die 108. In eitherconfiguration, e.g., one or more protrusions in direct contact with orin close proximity to a top of the die 106 A, however, heat generatedwithin the stack of die 106, 108 may be provided an enhanced thermalconduction path to the heat spreader 102 due to the proximity of theprotrusions 114 to the die 106 A and/or the exposed portions of the die108.

As heat moves from the stack of die 106 A-D and the die 108 to the heatspreader 102, the areas of the die 106 A and the exposed portions of thedie 108 under one or more of the protrusions 114 may be characterized ashaving increased thermal conductivity due to the reduction of thethermal interface layer 104 under the protrusions 114/heat spreader 102.Increased thermal conductivity may also be obtained when one or more ofthe protrusions 114 are in contact with the die 106A or the die 108.Thus, either or both situations—protrusions in close proximity to or incontact with a die surface—may provide enhanced heat dissipation for thecombination 100.

Thermal dissipation provided by the heat spreader 102 may further beenhanced due to increased surface area of the underside of the heatspreader 102 facing the stack of die 106, 108. The protrusions 114, forexample, may be pillars protruding from the underside of the heatspreader 102, with each pillar having a bottom surface and one or moreside surfaces, e.g., rectangular pillars or round pillars. The bottomsurface of each pillar, as discussed above, may either be in contactwith a die surface or in close proximity to the die surface such that avolume of the thermal interface layer is reduced between the die andpillar surface. The sides of each pillar may further improve the heatdissipation due to the increased surface area they provide for heatextraction by the heat spreader 102.

FIG. 1B is an example detailed view of a die, thermal interface layer,and heat spreader according to the present disclosure. The detailed viewmay include the heat spreader 102, one or more protrusions 114, thethermal interface layer 104, and the die 106 A. The thermal interfacelayer 104 is depicted to fill the space present between the die 106 Aand the heat spreader 102. Due to the protrusions 114, the thermalinterface layer 104 may be thinner, e.g., less volume, between theprotrusions 114 and the die 106 A than in the spaces between theprotrusions 114. Due to potential limitations of the thermalconductivity of the thermal interface layer 104, the protrusions 114 aredesigned to be disposed in, e.g., extend into or through, the thermalinterface layer so that they are in close proximity to and/or inconnection with a surface of the die 106A and the die 108. The reducedvolume of the thermal interface layer in these areas may increase heatdissipation by providing an improved heat path between the die and theheat spreader 102. An improved heat path may be characterized as areduction in distance heat may need to travel in a low thermalconductivity material, for example, the heat spreader 102.

The interface between the protrusions 114 and the die 106 A depicted inFIG. 1B (and FIG. 1A) is shown to include a layer of the thermalinterface layer 104 between the two components. Other orientations,however, are also contemplated by the present disclosure. For example,one or more protrusions 114 of the heat spreader 102 may be in contactwith the die 106A such that virtually no thermal interface layer 104 ispresent between the two components. Direct connection may furtherenhance heat dissipation. The detailed view shown in FIG. 1B in relationto a die 106A may also be descriptive of the relationship between theheat spreader, thermal interface layer, and die 108.

FIG. 2A is an example illustration of a heat spreader and semiconductordie stack combination 200 according to the present disclosure. Thecombination 200 may include many of the same features as does thecombination 100 of FIG. 1A, but differ in certain aspects. For example,the dies 208 A-D and the die 210 may include thermal dissipation pads206, which may enhance thermal path dissipation of the stack of die 208A-D and 210. The thermal dissipation pads may allow for increaseddissipation of heat from one or more of the die 208A-D, and/or the die210.

Similar to the heat spreader 102 of FIG. 1A, the heat spreader 202 mayinclude a plurality of protrusions 216. The plurality of protrusions 216may form an array or grid of protrusions on the underside, e.g., thesurface of the heat spreader 202 facing the stack of die 208. Theprotrusions 216 may also be described as internally-facing since theyextend internal to the combination 200 instead of external, as many heatsinks are designed. The die 208 A, and the die 210 may include aplurality of thermal dissipation pads 206, which may be laid out in agrid pattern on a top surface of at least those two die, e.g., thesurface of the die 208 A facing the heat spreader 202 as depicted inFIG. 2A. The dies 208 A-D, 210 may also include a plurality ofthrough-via conductors and associated bonding pads located on both topand bottom surfaces of the die (not shown), where the bonding pads maybe on the surfaces of the die 206A and the die 210 facing the heatspreader 202. The bonding pads associated with the plurality ofthrough-via conductors may be arranged in periodic columns and/or rows,and it may be desirable for the through-via conductors to not makecontact with any of the protrusions 216. Contact with any of theprotrusions 216 by any of the through-via bonding pads may short circuitat least part of the stack of die 208 A-D, 210. The heat spreader 202may be designed so that the plurality of protrusions 216 align with ormake contact to one or more of the thermal dissipation pads 206 whileavoiding the bonding pads for the through-via conductors.

The protrusions 216 may be in close proximity to one or more thermaldissipation pads 206 so that a reduced volume of the thermal interfacelayer 204 is disposed between one or more of the protrusions 216 and oneor more of the thermal dissipation pads 206. Alternatively oradditionally, one or more of the protrusions 216 may make direct,physical contact with one or more thermal dissipation pads 206. FIG. 2Adepicts a one-to-one relationship between a protrusion 216 and a thermaldissipation pad 206, which may be shown for clarity of discussion. Otherrelationships, however, may also fall within the scope of the presentdisclosure. For example, a protrusion 216 may be in close proximity toor in direct contact with more than one thermal dissipation pad 206.Moreover, a bottom face of a protrusion 216 may be in close proximity toor in direct contact with a small array or a plurality of thermaldissipation pads 206.

The connection between one or more protrusions 216 and one or morethermal dissipation pads 206 may be either direct physical contact dueto proximity or a metallic bond may be formed between the two. Thethermal dissipation pads 206 may be coated with or formed from one ormore metals. The one or more metals may be a metal stack that includescopper, nickel, and gold or palladium, for example. The protrusion-sideof the heat spreader 202 may be similarly coated. A eutectic bond maythen be formed between one or more of the thermal dissipation pads 206and one or more of the protrusions 216 by subjecting the combination 200to one or more heat treatments and or re-flow processes. The eutecticbond may further improve heat dissipation of the combination 200.

Thermal dissipation may improve whether or not one or more of thethermal dissipation pads 206 and one more of the protrusions 216 are indirect physical contact. For example, a reduction in volume of thethermal interface layer 204 between a protrusion 216 and a thermaldissipation pad 206 may provide improved thermal dissipation. Theimproved thermal dissipation may be due, at least in part, to animproved heat dissipation path between the die 208 A, and/or the die 210and the heat spreader 202. Additionally, there may be embodiments wherea subset of the plurality of protrusions 216 are in contact with one ormore thermal dissipation pads 206 while other protrusions are in closeproximity to one or more thermal dissipation pads 206.

FIG. 2B is an example detailed view of a die, thermal interface layer,and heat spreader according to the present disclosure. The detailed viewincludes the die 208 A, thermal dissipation pads 206, the thermalinterface layer 204, and protrusions 216 of the heat spreader 202. Thedetailed view may also represent the relationship between the designatedcomponents in relation to the edges of the die 210. The detailed viewdepicts the protrusions 216 and the thermal dissipation pads 206 asbeing in contact, e.g., direct physical contact. As noted, otherproximate relationships may exist between the protrusions 216 and thethermal dissipation pads 206, and all variations fall within the scopeof the present disclosure. For example, a thin layer of the thermalinterface layer 204 may be disposed between a protrusion 216 and athermal dissipation pad 206. Additionally, proximity of a protrusion toa thermal dissipation pad may be subject to variations due to variationsin the fabrication of the thermal dissipation pads, the heat spreaderprotrusions, the mounting process or combinations thereof.

FIG. 3 is an example illustration of a die 300 according to the presentdisclosure. The illustration of FIG. 3 may depict a back or top of adie. The die 300 may, for example, be used as one of the die 208 A-D,such as the die 208 A in the stack depicted in FIG. 2. The die 300 mayalso be an example of the die 210 of FIG. 2. The die 300 may have anarray of bonding pads formed on one surface, the backside surface of thedie 300 for example. The front side surface of the die 300 (not shown)may include the active region of the die, which may include circuitssuch as transistors and logic gates. The array of bonding pads mayinclude periodic columns of through-via bonding pads 302 along with aplurality of the thermal dissipation pads 304. The through-via bondingpads 302 are shown in FIG. 3 as darkened circles and the thermaldissipation pads 304 are shown as unfilled circles. The through-viabonding pads 302 may provide electrical connections to the front sidesurface of the die 300 from the backside surface. Further, multiple diemay be stacked on top of one another and the through-via bonding pads302 (along with through-via conductors) allow for the stack of die to beelectrically interconnected by a common data/command bus, for example.The thermal dissipation pads 304 may be disposed on a passivation layercoating the backside surface of the die 300, for example. The thermaldissipation pads 304 may provide thermal dissipation pathways inaddition to structural support for a stack of die.

The thermal dissipation pads 304 may be formed from one or more metals,such as a stack of copper, nickel, and gold. In some examples, palladiumis used instead of gold. The one or more metals used to form the thermaldissipation pads 304 may be similar to the one or more metals used toform the through-via bonding pads 302. The array pattern the bondingpads shown for the die 300 in FIG. 3 are for illustrative purposes onlyand any pattern falls within the scope of the present disclosure.

The layout of the thermal dissipation pads 304 and the through-viabonding pads 302 may determine a layout and design configuration forheat spreader protrusions. Because it may be desirable to avoid contactbetween heat spreader protrusions and through-via bonding pads 302, heatspreader protrusions may be designed so that one or more spaces betweenthe protrusions align with the through-via bonding pads 302 when theheat spreader is mounted onto a stack of die, as depicted in FIG. 2A.With regards to the thermal dissipation pads 304, however, it may bebeneficial for the heat spreader protrusions to correspond with one ormore thermal dissipation pads after mounting. With the thermaldissipation pads 304 and heat spreader protrusions in alignment, theheat dissipation path for one or more die may be enhanced.

FIGS. 4A and 4B are illustrative examples of a heat spreader 400according to the present disclosure. The heat spreader 400 may be anexample of the heat spreader 102 of FIG. 1A and/or the heat spreader 202of FIG. 2A. A view from the underside of the heat spreader 400 is shownin FIGS. 4A and 4B. The heat spreader 400 may be formed by a body 402that may be U or horseshoe-shaped and that includes a plurality ofprotrusions 404. The plurality of protrusions 404 may be formed on theunderside of the body 402 in the areas 406 and 408. By forming theprotrusions 404 on the underside of the body 402, the protrusions may beinternally or die facing, such as depicted in FIGS. 1A and 2A, when theheat spreader 400 is mounted on a die stack. The protrusions 404 aredepicted as rectangular pillars, but any shape falls within the scope ofthe current disclosure. For example, the protrusions 404 may becylindrical or triangular, e.g., prism-shaped. A bottom face of theprotrusions 404 may be from 50 microns on a side to 0.5 mm on a side.The height of the protrusions may be similarly sized. The spacingbetween the protrusions may either be of similar dimensions or may bebased on the pitch and size of an array of thermal dissipation pads. Assuch, each protrusion may be depicted as a small pillar formed on orfrom the body 402. Further, each protrusion may of a different shapeand/or size, which may depend on a design of a die which a heat spreader400 is to be mounted.

The number and shape of the protrusions may vary based on the design ofthe die that the heat spreader may be mounted upon, e.g., die with andwithout thermal dissipation pads. Further, the spacing between the diemay also vary based on heat spreader size, die size/design, protrusionsize, or combinations thereof. The size, shape, number, and layout ofthe protrusions, any of which fall within the scope of the presentdisclosure, may at least be driven by thermal dissipation improvement.

A thermal interface layer deposed between a die and a heat spreader,such as the thermal interface layers 104 and 204 of FIGS. 1A and 2A,respectively, may also influence the design of the heat spreaderprotrusions. Stress-induced delamination of the thermal interface layermay be a concern and may occur where the thermal interface layerthickness does not allow for stress relief due to the thickness beingtoo thin to allow for deformation of the layer. Further, stress-induceddelamination may occur at the edges of a thin film where the stress maybe relieved by the thin film releasing from a substrate, the die surfacefor example, instead of deforming. To assist with stress relief, theprotrusions may be offset from the very edge of a die so that thethermal interface layer at the edges is thick enough to allow for stressrelief. Further stress relief may occur in the spaces between theprotrusions where the thermal interface layer is thicker. As such, aplurality of protrusions may allow the thermal interface layer torelieve planar stress to reduce delamination within spaces between theprotrusions.

Since the heat spreader 400 may also be a conformal lid for a stack ofdie, the heat spreader 400 may take the U-type shape as depicted in FIG.4B. The U-type shape may be used so that the heat spreader 400 is inclose proximity with or contact with the top die in a stack, such as thedie 106A of FIG. 1, and so the ledges 408 are close to the exposed edgesof a bottom die, such as the die 210 of FIG. 2A. Further, due to the lidconforming to the stack of die, the heat dissipation path is furtherreduced. Other mechanical and structural advantages may be obtained fromthe heat spreader 400, which would be clear to one skilled in the art.The U-type shape depicted in FIG. 4B shows protrusions located on area406 of the body 402 and the ledges 408 of the body 402. The area 406,for example, may, after mounting the heat spreader 400 to a stack ofdie, align with a top die of a stack, such as the die 106A of FIG. 1A orthe die 208A of FIG. 2A. The ledges 408 may align with the exposedregions of the die 108 of FIG. 1A or the die 210 of FIG. 2A.

The heat spreader 400 may be fabricated by various methods and the sizeof the protrusions may determine the method used for their fabrication.The U-type shape of the heat spreader 400 may be formed through astamping process and the protrusions may be formed during the stampingprocess or by additional fabrication steps. For example, if the bottomsurface of each of the protrusions are 0.5 mm on a side, then the heatspreader including the protrusions may be fabricated using aconventional metal stamping process. If, however, the protrusions 404are smaller, around 50 microns on a side for example, then the heatspreader body 402 may be stamped and the protrusions 404 formed throughmasking and etching. Additionally, if eutectic bonds are to be formedwith thermal dissipation pads, for example, then the heat spreader, orat least bottom face of the protrusions 404, may be coated with a metal,such as gold or tin. Tolerances and variations in the heat spreader 400fabrication process may influence whether or not the protrusions 404make contact with a die and/or a thermal dissipation pad of a die. Theheight of the protrusions may be designed to target contact, butprotrusions that are shorter due to fabrication process variation maystill be substantially close to the die and/or thermal dissipation padsto improve heat dissipation characteristics of the heat spreader 400.

The heat spreader 400 die mounting process may include dispensing athermal interface layer material onto the top of the die stack, such asthe top of the die 208A and the exposed edges of the die 210 of FIG. 2A,followed by pressing the heat spreader 400 down onto the die stack. Thepressing of the heat spreader onto the die stack may cause the thermalinterface layer material to flow into a thin layer that covers the diestack and which also fills the interstitial areas between theprotrusions 404. If a eutectic bond between the protrusions and thermaldissipation pads is desired, then the combination of the die stack andheat spreader may be subjected to one or more heat treatments to formthe bonds.

The die stacks depicted in FIGS. 1A and 2A are for illustrative purposesonly and are not limiting. All possible variations in the number of diein the stack and the types of die in the stack are within the scope ofthe present disclosure. For example, an interposer die may be insertedbetween a die 108 and the bottom die 106, for example, which may providefurther structural stability and thermal enhancement.

From the foregoing it will be appreciated that, although specificembodiments of the disclosure have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the disclosure. Accordingly, the disclosure isnot limited except as by the appended claims.

1. An apparatus, comprising: a substrate; a thermal interface layerdisposed on a surface of the substrate; and a heat spreader including aplurality of substrate-facing protrusions in contact with the thermalinterface layer, wherein the plurality of substrate-facing protrusionsare disposed at least partially through the thermal interface layer. 2.The apparatus of claim 1, wherein the plurality of substrate-facingprotrusions are disposed through the thermal interface layer and are incontact with the substrate.
 3. The apparatus of claim 1, wherein asubset of the plurality of substrate-facing protrusions are disposedthrough the thermal interface layer and are in contact with thesubstrate.
 4. The apparatus of claim 1, wherein a thickness of thethermal interface layer under a face of the plurality ofsubstrate-facing protrusions facing the substrate is thinner relative toa thickness of the thermal interface layer under areas of the heatspreader that have no substrate-facing protrusions.
 5. The apparatus ofclaim 1, wherein the plurality of substrate-facing protrusions form anarray of protrusions.
 6. The apparatus of claim 1, wherein the substratefurther includes a plurality of thermal dissipation pads, and wherein asubstrate-facing protrusion of the plurality of substrate-facingprotrusions is in contact with one or more of the plurality of thermaldissipation pads.
 7. The apparatus of claim 1, wherein the plurality ofsubstrate-facing protrusions are disposed through the thermal interfacelayer and are in substantially close proximity with the substrate with asmall volume of the thermal interface layer between a bottom face ofeach of the plurality of substrate-facing protrusions and the substrate.8. The apparatus of claim 1, wherein the substrate is a semiconductordie.
 9. The apparatus of claim 8, wherein the semiconductor die is amemory die.
 10. An apparatus, comprising: a substrate including aplurality of thermal dissipation pads on a surface of the substrate; athermal interface layer disposed on the surface of the substrate thatincludes the plurality of thermal dissipation pads; and a heat spreaderincluding a plurality of internally-facing protrusions, wherein a distalend of the plurality of internal-facing protrusions are disposed in thethermal interface layer.
 11. The apparatus of claim 10, wherein thedistal end of the plurality of internally-facing protrusions are incontact with a thermal dissipation pad of the plurality of thermaldissipation pads.
 12. The apparatus of claim 10, wherein the pluralityof thermal dissipation pads and the plurality of internally-facingprotrusions are aligned.
 13. The apparatus of claim 10, wherein theplurality of thermal dissipation pads are arranged in an array on thesurface of the substrate.
 14. The apparatus of claim 10, wherein theplurality of thermal dissipation pads includes a through-via bondingpad.
 15. The apparatus of claim 14, wherein the plurality ofinternally-facing protrusions form an array and spaces between a subsetof the plurality of internally-facing protrusions align with athrough-via bonding pad.
 16. The apparatus of claim 10, wherein aeutectic bond is formed between one or more of the plurality ofinternally-facing protrusions and one or more of the plurality ofthermal dissipation pads.
 17. The apparatus of claim 10, wherein thesubstrate is a top die of a stack of semiconductor die, wherein a bottomdie of the stack of semiconductor die extends beyond one or more of theother die in the stack of semiconductor die and includes an exposedportion.
 18. The apparatus of claim 17, wherein the exposed portion ofthe bottom die includes a plurality of thermal dissipation pads, andwherein one or more of the internally-facing protrusions are in closeproximity to or in contact with the exposed portion of the bottom dieincluding one or more of the plurality of thermal dissipation pads. 19.An apparatus, comprising: a heat spreader including a plurality ofprotrusions formed on a bottom side of the heat spreader; and a die; athermal interface layer disposed on a surface of the die; wherein theheat spreader is disposed on the die with the thermal interface layerbetween the bottom side of the heat spreader and the surface of the die,and wherein the plurality of protrusions are imbedded, at leastpartially, into the thermal interface layer.
 20. The apparatus of claim19, wherein one or more of the plurality of protrusions extend throughthe thermal interface layer and are in contact with the surface of thedie.
 21. The apparatus of claim 19, wherein the die further includes anarray of thermal dissipation pads formed on the surface of the die. 22.The apparatus of claim 21, wherein a protrusion of the plurality ofprotrusions is in close proximity to a thermal dissipation pad of theplurality of thermal dissipation pads.
 23. The apparatus of claim 21,wherein one or more of the plurality of protrusions are in contact withone or more of the plurality of thermal dissipation pads.
 24. Theapparatus of claim 19, wherein the heat spreader comprises a conformallid.
 25. The apparatus of claim 24, further comprising other die to forma stack of die and the heat spreader forms part of a package for thestack of die.